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The pressure-induced emission (PIE) behavior of halide perovskites has attracted widespread attention and has potential application in pressure sensing. However, high-pressure reversibility largely inhibits practical applications. Here, we describe the emission enhancement and non-doping control of the color temperature in two-dimensional perovskite (C6 H5 CH2 CH2 NH3 )2 PbCl4 ((PEA)2 PbCl4 ) nanocrystals (NCs) through high-pressure processing. A remarkable 5 times PIE was achieved at a mild pressure of 0.4 GPa, which was highly associated with the enhanced radiative recombination of self-trapped excitons. Of particular importance is the retention of the 1.6 times emission of dense (PEA)2 PbCl4 NCs upon the complete release of pressure, accompanied by a color change from "warm" (4403 K) to "cold" white light with 14295 K. The irreversible pressure-induced structural amorphization, which facilitates the remaining local distortion of inorganic Pb-Cl octahedra with respect to the steric hindrance of organic PEA+ cations, should be greatly responsible for the quenched high-efficiency photoluminescence.

SiO2 is the major mineral substance in the upper mantle of the earth. Therefore, studies of the silica-coated materials under high-pressure are essential to explore the physical and chemical properties of the upper mantle. The silica-confined CsPbBr3 nanocrystals (NCs) have recently attracted much attention because of the improved photoluminescence (PL) quantum yield, owing to the protection of silica shell. However, it remains considerable interest to further explore the relationship between optical properties and the structure of CsPbBr3@SiO2 NCs. We systemically studied the structural and optical properties of the CsPbBr3@SiO2NCs under high pressure by using diamond anvil cell (DAC). The discontinuous changes of PL and absorption spectra occurred at ∼1.40 GPa. Synchrotron X-ray diffraction (XRD) studies of CsPbBr3@SiO2 NCs under high pressure indicated an isostructural phase transformation at about 1.36 GPa, owing to the pressure-induced tilting of the Pb-Br octahedra. The isothermal bulk moduli for two phases are estimated about 60.0 ​GPa and 19.2 GPa by fitting the equation of state. Besides, the transition pressure point of CsPbBr3@SiO2 NCs is slightly higher than that of pristine CsPbBr3 NCs, which attributed to the buffer effect of coating silica shell. The results indicate that silica shell is able to enhance the stabilization without changing the relationship between optical properties and structure of CsPbBr3 NCs. Our results were fascinated to model the rock metasomatism in the upper mantle and provided a new ‘lithoprobe’ for detecting the upper mantle.

By employing heat rather than mechanical work to compress the working fluid, the thermal compression CO2 Brayton cycle (TC-CBC) has been considered as a promising pathway to the efficient utilization of low-grade thermal energy. However, finding reasonable adsorbents to efficiently realize the thermal compression process via the CO2 adsorption–desorption loop has become a significant challenge to the development of such an innovative system. To solve the dilemma, high-throughput computational screening based on grand canonical Monte Carlo (GCMC) simulations and machine learning (ML) have been conducted to identify promising adsorbents from 1625 metal–organic frameworks (MOFs) for the TC-CBC. Results demonstrate that the thermodynamic efficiency and output per unit mass adsorbent of the system with a low-temperature heat source at 393 K can reach up to 9.34% and 21.84 kJ kg−1, respectively. MOFs with large surface area, pore volume, porosity, and moderate pore size have exhibited high thermodynamic performances. In addition to the low-temperature heat source, a high-temperature heat source is also considered in the analysis. The elevation of the thermodynamic performance is observed to be dependent on the structural properties of MOFs. With a random forest algorithm, a rapid and accurate prediction of thermodynamic performances for the innovative cycle is achieved.

Lead halide two-dimensional (2D) nanomaterials (NCs) have attracted continuous attention owing to their unique optoelectronic properties. However, the toxicity of lead largely prevents their commercialization. Therefore, environmentally friendly lead-free 2D perovskite NCs are sorely needed in the aspects of application. Recently, 2D lead-free halide perovskite Cs3Bi2Br9 NCs have attracted intense attention because of their environmentally friendly and potentially useful photovoltaic behavior. In this work, we explored the structure–property relationship of Cs3Bi2Br9 NCs by using high pressure techniques. The band gap of Cs3Bi2Br9 NCs was narrowed by about 0.69 eV, originating from Bi–Br bond contraction and Br–Bi–Br bond angle changes in the [BiBr6]3− octahedra. Angle dispersive synchrotron X-ray diffraction patterns and Raman spectra show that the Cs3Bi2Br9 NCs experienced a phase transition from the trigonal phase to monoclinic phase, and then amorphization with increasing pressure. The results also indicate that the changes are reversible after pressure relief. First-principles calculations further demonstrate that the band gap is largely influenced by the orbital interactions, which is related to the distortion of the Bi–Br octahedral network under pressure. Our research not only strengthens the basic understanding of Cs3Bi2Br9 NCs, but also enables pressure processing as an efficient and environmentally friendly strategy to improve the application of design-by-design materials.

Developing single-component materials with bright-white emission is required for energy-saving applications. Self-trapped exciton (STE) emission is regarded as a robust way to generate intrinsic white light in halide perovskites. However, STE emission usually occurs in low-dimensional perovskites whereby a lower level of structural connectivity reduces the conductivity. Enabling conventional three-dimensional (3D) perovskites to produce STEs to elicit competitive white emission is challenging. Here, we first achieved STEs-related emission of white light with outstanding chromaticity coordinates of (0.330, 0.325) in typical 3D perovskites, Mn-doped CsPbBr3 nanocrystals (NCs), through pressure processing. Remarkable piezochromism from red to blue was also realized in compressed Mn-doped CsPbBr3 NCs. Doping engineering by size-mismatched Mn dopants could give rise to the formation of localized carriers. Hence, high pressure could further induce octahedra distortion to accommodate the STEs, which has never occurred in pure 3D perovskites. Our study not only offers deep insights into the photophysical nature of perovskites, it also provides a promising strategy towards high-quality, stable white-light emission., We first achieved self-trapped exciton emission with outstanding white-light chromaticity coordinates of (0.330, 0.325) in conventional 3D halide perovskite nanocrystals through pressure engineering.

The origin of green emission in the zero-dimensional (0D) perovskite Cs4PbBr6 nanocrystals (NCs) remains a considerable debate. Herein, an approach involving a combination of high-pressure experime...

The exploration of water-retention hydrogels is of great significance for electronics, tissue engineering, biomedical devices, and various fields that rely on hydrogels as platforms. However, the development of efficient water retention hydrogels still encounters severe challenges despite a series of proposed design principles. Here, we try to explore moisturizing hydrogels and evaluate the water retention capability from the perspective of color signal conservation considering its visualization feature. An interpenetrating hydrogel with an alternating hydrophilic and hydrophobic structure constructed by micelles and rigid chains was proposed from the perspective of manipulating the water state through chain state and inter-segment interaction forces brought by the hydrogel network. Due to the efficient reduction of the kinetic activation energy brought by the strong bonding of water molecules to the hydrophilic polymer chain and the repelling effect of water molecules to the wrinkled corners by the hydrophobic chain, remarkable water anchoring ability was achieved. The proposed water retention strategy was evidenced by the remarkably restricted color diffusion of dye particles and the reaction product resulting from the specific probe molecules with urea particles. We expect that the present water anchoring design strategy would open up a brand-new methodology for the exploration of high-performance moisturizing hydrogels and efficient colorimetric hydrogel devices.

A bright difluoroboron β-diketonate derivative 1 showing four emission colors (green, yellow, orange and red) with high quantum yields (41–74%) in four polymorphs and one amorphous state is reported. Green-emissive crystals (1-G and 1-G′) exhibit dimeric aggregation structures due to the strong molecular π–π interaction but exhibit hypsochromic emission compared to yellow-emissive crystals (1-Y) with monomeric aggregation because of lacking such π–π interactions. These novel emission phenomena are rationalized by theoretical calculations. High fluorescence sensitivity of compound 1 to its molecular packing modes results in excellent responsive behavior to multiple external stimuli thereby showing reversible change of emission colors under mechanical grinding, heating, solvent fuming and hydrostatic pressure.

Halide perovskites have attracted great attention owing to their outstanding performance in optoelectronic applications and solar cells. Recently, two-dimensional (2D) Cs3Sb2I9 nanocrystals (NCs) have attracted sustained interest due to their potentially useful photovoltaic behavior. However, their practical application is impeded by the large bandgap. In this study, the bandgap of 2D Cs3Sb2I9 NCs is successfully narrowed from 2.05 eV to 1.36 eV by means of a high pressure with a measurable rate of 33.7%. Optical changes of 2D Cs3Sb2I9 NCs originate from Sb–I bond contraction and I–Sb–I bond angle changes within the [SbI6]3− octahedra, which determines the overlap of orbitals. Angle dispersive synchrotron X-ray diffraction spectra and Raman spectra of Cs3Sb2I9 NCs indicate that the structural amorphization gradually begins at about 14.0 GPa and the changes are reversible once pressure is completely released. The band gap is slightly smaller after decompression than that under the initial ambient conditions, resulting from the incomplete recrystallization process. First-principles calculations further elucidate that variations in band gaps are mainly governed by the orbital interactions associated with the distortion of the Sb–I octahedral network upon compression. The research enhances the fundamental understanding of 2D Cs3Sb2I9 NCs and is expected to greatly advance the research progress of perovskites in band gap interception at high pressures. Meanwhile, this study demonstrates that pressure processing can be used as a robust strategy to improve materials-by-design in applications.

The high-pressure behavior of three-dimensional (3D) metal halide perovskites (MHPs) has been extensively studied. Prior to the means of high-pressure fever, most experimental efforts to study the structure and optical behavior of 3D MHPs focused on dopants and dimensional reduction. The structure and properties of 3D MHPs can be regulated in situ and continuously controlled by applying high pressure, which cannot be achieved with traditional chemical methods. In this review, recent progress on studies on the response to pressure of the structure, optical properties, and carrier dynamics of 3D MHPs was summarized. The underlying mechanism of the high-pressure behavior of 3D MHPs was discussed comprehensively. Future research directions on 3D MHPs were also outlined to guide further investigations. This review aimed to provide a basis for facilitating the understanding of timely developments in emerging high-pressure perovskite-related research fields.

Fatigue of superelastic Nitinol in the mixed austenite–martensite state was examined in tension using center-tapered dog-bone specimens. A prestraining procedure, mimicking the load history of a medical device component, was applied prior to cycling: specimens were loaded to a fully martensitic state, unloaded partway into the lower plateau to a mixed-phase state, and then subjected to sinusoidal displacement cycles. Strain maps, obtained using digital image correlation, showed substantial variation in local mean and alternating strains across the gage section. In situ surface imaging using a high-speed camera confirmed crack initiation in a narrow transition zone between austenite and martensite that undergoes cyclic stress-induced martensitic transformation (SIMT). Fatigue life data showed an abrupt transition from high-cycle runouts to low-cycle fatigue failures at a stress amplitude level corresponding to the threshold for activating cyclic SIMT. The fatigue threshold can be estimated from the tensile loading–unloading curve.

Crystallographic dislocation has been well-known to be one of the major causes responsible for the unfavorable carrier dynamics in conventional semiconductor devices. Halide perovskite has exhibited promising applications in optoelectronic devices. However, how dislocation impacts its carrier dynamics in the ‘defects-tolerant’ halide perovskite is largely unknown. Here, via a remote epitaxy approach using polar substrates coated with graphene, we synthesize epitaxial halide perovskite with controlled dislocation density. First-principle calculations and molecular-dynamics simulations reveal weak film-substrate interaction and low density dislocation mechanism in remote epitaxy, respectively. High-resolution transmission electron microscopy, high-resolution atomic force microscopy and Cs-corrected scanning transmission electron microscopy unveil the lattice/atomic and dislocation structure of the remote epitaxial film. The controlling of dislocation density enables the unveiling of the dislocation-carrier dynamic relation in halide perovskite. The study provides an avenue to develop free-standing halide perovskite film with low dislocation density and improved carried dynamics., Crystallographic dislocation has proven harmful to the carrier dynamics in conventional semiconductors but it is unexplored in metal halide perovskites. Here Jiang et al. grow remote epitaxial perovskite films on graphene with density-controlled dislocations and confirm their negative impact.

Zinc blende cadmium selenide nanocrystals (Zb-CdSe NCs) were found to exhibit excellent photostability and high quantum yield compared with wurtzite (Wz) CdSe NCs, although Wz-CdSe NCs are more sta...

Pressure-induced emission (PIE) is extensively studied in halide perovskites or derivative hybrid halides. However, owing to the soft inorganic lattice of these materials, the intense emission is barely retained under ambient conditions, thus largely limiting their practical applications in optoelectronics at atmospheric pressure. Here, remarkably enhanced emission in microtubules of the 0D hybrid halide (C5 H7 N2 )2 ZnBr4 ((4AMP)2 ZnBr4 ) is successfully achieved by means of pressure treatment at room temperature. Notably, the emission, which is over ten times more intense than the emission in the initial state, is retained under ambient conditions upon the complete release of pressure. Furthermore, the pressure processing enables the tuning of "sky blue light" before compression to "cool daylight" with a remarkable quantum yield of 88.52% after decompression, which is of considerable interest for applications in next-generation lighting and displays. The irreversible electronic structural transition, induced by the steric hindrance with respect to complexly configurational organic molecules [4AMP], is highly responsible for the eventual retention of PIE and tuning of the color temperature. The findings represent a significant step toward the capture of PIE under ambient conditions, thus facilitating its potential solid-state lighting applications.

Two-dimensional (2D) lead halide perovskites are becoming attractive due to their exceptional stability and fine-tuning of optoelectronic properties compared to their 3D counterparts. Here, we systemically investigated the relationship between the structure and optical properties of 2D layered perovskite (C(NH2)3)(CH3NH3)2Pb2I7 under a high pressure. The emission intensity significantly increased as the pressure increased to 1.3 GPa, followed by a continuous reduction and disappearance at 7.0 GPa. Simultaneously, the bandgap first decreased, then increased, and gradually decreased again along with pressure elevation and was partially retainable after decompression due to structure recrystallization. The XRD result showed that the structure was stable up to 7.0 GPa and then gradually amorphized with local structure distortion. We speculated two distinct regimes of compression dominated by the alternating ordering of softer organic cation layers and less compressible inorganic octahedral layers. This work paves the way to investigate structure–property relationships in 2D perovskites and offers new strategies for further development of advanced perovskite devices.

Lead-free double halide perovskite nanocrystals (NCs) are attracting increasing attention due to their non-toxic nature and exceptional stability as a substitute material for lead-based perovskites. Herein, we investigate the relationship between the structural and optical properties of double halide perovskite Cs2AgBiBr6 NCs under high pressure. In situ synchrotron high-pressure powder X-ray diffraction and Raman experiments indicated that the structure of Cs2AgBiBr6 NCs transformed into a tetragonal from a cubic system at 2.3 GPa. Pressure-dependent absorption demonstrated that the band gap changes in the sequence red-shift → blue-shift. First-principles calculations further indicated that the band gap evolution was highly related to the orbital interactions, associated with the tilting and distortion of [AgBr6]5− and [BiBr6]3− octahedra under pressure. It is worth noting that the quenched absorption peak of Cs2AgBiBr6 NCs was slightly blue-shifted compared with that of the initial one under ambient conditions, which is in stark contrast to that of the corresponding bulk counterparts. This is because the structure of the sample was not yet recovered and maintained a certain degree of distortion after fully releasing the pressure. What's more, the NCs after decompression are a mixture of cubic and tetragonal phases, which leads to a larger quenched band gap than that of the initial value. Our results improve the understanding of the structural and optical properties of nanostructured double halide perovskites, thus providing a basis for their application in optoelectronic devices.

Here, we report the structural stability and visible light response of two-dimensional (2D) layered perovskite-like CsPb2Br5 microplates (MPs) under high pressure. In situ high-pressure emission, optical absorption, and angle dispersive synchrotron X-ray diffraction indicated that CsPb2Br5 MPs experienced an isostructural phase transformation at roughly 1.6 GPa. The shrinkage of Pb–Br bond lengths and the marked change of Br–Pb–Br bond angles within the lead-bromide pentahedral motif were responsible for the pressure-induced structural modulation and the sudden band-gap change of CsPb2Br5 MPs.

The photoluminescence (PL) mechanism plays a significant role in the study of carbonized polymer dots (CPDs). The supramolecular interaction exists in most materials, which offers innate methods to regulate the optical and physical properties. However, insights into the tunable red- and blue-shifted PL peaks of CPDs by the supramolecular interaction still remain elusive. Herein, the supramolecular interaction-triggered fluorescence change of CPDs is reported by the investigation of the piezochromic behaviors. The π-conjugated system and the hydroxy group are both critical to manipulate the PL of CPDs under high pressure. The π-π stacking of the π-conjugated system was enhanced with increasing pressure, which induces the red-shifting of PL peaks, while the hydroxyl-related hydrogen bond formation eventually causes a blue-shift. In addition, their chemical stability, low toxicity, and the tunable PL properties of CPDs by supramolecular interaction under high pressure would deepen the understanding of the fluorescence mechanism of CPDs, inspiring extensive application prospects in sensing and light-emitting diodes.

The present paper investigated the seasonal solar thermal energy storage (SSTES) using solid-gas thermochemical sorption technology that has inherently combined function of heat pump and energy storage. The thermochemical reactions that can discharge heat at a higher temperature usually requires a relatively higher desorption temperature during charging process, which could be problematic to efficiently recover solar energy in high-latitude regions like the UK when using the most mature and economic solar thermal collector (flat-plate or evacuated tube type). The present work studied two hybrid concepts where an electric-driven compressor or an electric heater was introduced to supplement the thermochemical desorption process in terms of pressure rise and temperature lift, respectively, when the available solar heat was not sufficiently high. The SrCl2-8/1NH3 chemisorption was selected from 230 ammonia-chemisorption reactions due to its suitable adsorption/desorption temperature and large energy storage density. The performance of two hybrid systems using SrCl2-8/1NH3 chemisorption were evaluated and compared to determine the optimal solution. The results revealed that the hybrid thermochemical sorption with a compressor substantially improved the storage capacity compared to that with electric heater. With a compression ratio of 4, the SSTES system with 20 m2 solar collector under the weather condition of Newcastle upon Tyne can store 3226.8 kWh chemisorption heat in summer by charging 4465.4 kWh solar heat and 848.2 kWh electricity, indicating 60.7% storage efficiency; the corresponding energy density based on the overall system volume is 147.3 kWh/m3. Because of using the renewable solar heat and low carbon intensity electricity in summer, the proposed hybrid SSTES system has noteworthy reduction on carbon emission compared to gas boiler and conventional heat pump.

A gradient nano- and submicron-structured surface layer of SIMP steel was produced by means of shot peening (SP). Compared with the original samples, corrosion experiments at 550℃ for various durations (120 h-1218 h) in liquid LBE showed that the oxidation resistance of the SP samples is significantly improved by shot peening, owing to the enhanced diffusivity of Cr by the large number of grain boundaries and dislocations introduced by shot peening, making it easier to form enhanced Cr-rich oxides. The magnetite layer of the SP samples has higher compactness, giving it better resistance to exfoliation than that of CG samples.

Irradiation damage on corrosion process of steels in Pb or LBE melts is a main challenge for the R&D of LFR. In this paper, A martensitic steel (SIMP) was in-situ irradiated with 247 MeV Ar ions while simultaneously exposed to flowing molten LBE to investigate the effect of irradiation on the structure of surface oxides. The results showed that ion irradiation not only accelerated the LBE corrosion, but also modified the structure of surface oxides significantly. Possible mechanism was proposed to help understand the microstructure evolution of oxides under simultaneous irradiation and corrosion.

Metal halide perovskites (MHPs) have attracted increasing research attention given the ease of solution processability with excellent optical absorption and emission qualities. However, effective strategies for engineering the band gap of MHPs to satisfy the requirements of practical applications are difficult to develop. Cubic cesium lead iodide (α-CsPbI3), a typical MHP with an ideal band gap of 1.73 eV, is an intriguing optoelectric material owing to the approaching Shockley–Queisser limit. Here, we carried out a combination of in situ photoluminescence, absorption, and angle-dispersive synchrotron X-ray diffraction spectra to investigate the pressure-induced optical and structural changes of α-CsPbI3 nanocrystals (NCs). The α-CsPbI3 NCs underwent a phase transition from cubic (α) to orthorhombic phase and subsequent amorphization upon further compression. The structural changes with octahedron distortion to accommodate the Jahn–Teller effect were strongly responsible for the optical variation with the...

In the present study, Ti3AlC2 samples were irradiated at room temperature by Fe ions, He ions, sequential Fe and He ions. Our results demonstrate the evolution of irradiation defects with the damage level and sequential two sorts of ions irradiation. A large number of stacking faults and a small amount of twins are formed under the damage level of ∼8 displacements per atom during Fe ions irradiation. The former contributes much to the formation of the latter. In the sequential irradiated samples, the following He ions irradiation promotes a further evolution of the defects induced by Fe ions irradiation resulting in significant decreases in the intensity of GIXRD; the fluence of 1 × 1016 He/cm2 gives rise to a high density of dislocation loops parallel to the basal plane and meanwhile a few of He bubbles are observed.

Tungsten alloy balls are considered as one of the important candidate spallation targets for China initiative Accelerator Driven Subcritical System. The wear of these balls in the spallation target loop greatly affects their service life. In this work, the collective friction and wear of the balls at 250 °C were studied by using our self-developed equipment. The results reveal that the mass loss ratio of balls first rises and then falls, experiencing different stages, and its maximum is about 0.32 wt%. For each stage balls have their own unique wear characteristics. In the end a new layer with a structure of amorphous surrounding nanocrystallines is formed on the ball surface. The role of wear debris in the all process is discussed.

Behaviors of body centered cubic (bcc) Fe(100)-liquid lead-bismuth eutectic (LBE) solid-liquid interface have been studied by classical molecular dynamics simulation (MD) with embedded-atom model potential under anaerobic conditions. Both static and dynamic simulation results indicate that Fe atoms prefer to bind with Bi atoms rather than Pb atoms. Trajectories of Bi and Pb perpendicular to the interface show obvious thermal vibrations of both liquid components at the time scale of about 0.9 ns for atoms Bi, and about 0.3 ns for atoms Pb, respectively. Temperature effect on penetration of liquid atoms into bulk Fe and dissolution of Fe into liquid in the solid-liquid interface system show that interactions between the bcc Fe(100) and liquid LBE mount perceptibly in the temperature range of 823 to 873 K. This result indicates that the critical temperature of the interaction between the bcc Fe(100) and liquid LBE is between 823 K and 873 K, which is consistent with the designed operating temperature for LBE coolant.

Cold embrittlement is one of the primary concerns challenging the usage of steels in infrastructures like pipelines and ocean platforms. This challenge is also compounded by the limited selection of materials for application in a cold and corrosive environment. Inspired by recent progresses in developing gradient structured materials with extraordinary properties, here we report a class of stainless steels with gradient phase structures achieving a superb combination of strength (1753 MPa) and tensile ductility (>25%) at the cryogenic temperature of 77 K. A set of cylindrical steel samples acquire a graded mixture of hard martensitic and soft austenitic phases through pre-torsion, which results in an optimal stress partition in the material - the hard martensitic structures showing a positive density gradient from core to edge carry higher stress near the edge, while the soft austenitic phase showing a negative density gradient from core to edge serves to retain substantial tensile ductility. The phase-transformation at low temperature in gradient structures and the resulted work-hardening could be adopted to enhance the ductility and strength of widely used engineering materials for their applications in harsh environment.

The injectable hydrogel is an ideal reservoir for drug delivery. In this study, a new injectable DNA hydrogel was fabricated. Firstly, the DNA pre-gel was obtained by heat-cool treatments to induce cross-linkage through base-paring. Then, the pre-gel was cross-linked with chitosan (CS) through electrostatic interaction, which was confirmed by ATR-FTIR and XPS analysis. The DNA-CS hybrid gel showed finely tunable various properties such as porosity and viscosity. To simulate the biomedical application, the dexamethasone (Dex) was loaded into the gel and coated onto titanium implant surface to induce macrophages M2 polarization. Due to the excellent biocompatibility and Dex delivery, the decorated implant surface was favorable for RAW264.7 cells growth and showed powerful effects of inducing M2 polarization both in vitro and in vivo. In conclusion, it is the first report of DNA hydrogel synthesis via CS cross-linkage and the injectable DNA-CS hybrid gel was superb for therapeutic delivery.

The present paper aims at exploring a hybrid absorption-compression heat pump (HAC-HP) to upgrade and recover the industrial waste heat in the temperature range of 60°C–120°C. The new HAC-HP system proposed has a condenser, an evaporator, and one more solution pump, compared to the conventional HAC-HP system, to allow flexible utilization of energy sources of electricity and waste heat. In the system proposed, the pressure of ammonia-water vapor desorbed in the generator can be elevated by two routes; one is via the compression of compressor while the other is via the condenser, the solution pump, and the evaporator. The results show that more ammonia-water vapor flowing through the compressor leads to a substantial higher energy efficiency due to the higher quality of electricity, however, only a slight change on the system exergy efficiency is noticed. The temperature lift increases with the increasing system recirculation flow ratio, however, the system energy and exergy efficiencies drop towards zero. The suitable operation ranges of HAC-HP are recommended for the waste heat at 60°C, 80°C, 100°C, and 120°C. The recirculation flow ratio should be lower than 9, 6, 5, and 4 respectively for these waste heat, while the temperature lifts are in the range of 9.8°C–27.7 °C, 14.9°C–44.1 °C, 24.4°C–64.1°C, and 40.7°C–85.7°C, respectively, and the system energy efficiency are 0.35–0.93, 0.32–0.90, 0.25–0.85, and 0.14–0.76.

Small-scale organic Rankine cycle (ORC) systems driven by solar energy are compared in this paper, which aims to explore the potential of power generation for domestic utilisation. A solar thermal collector was used as the heat source for a hot water storage tank. Thermal performance was then evaluated in terms of both the conventional ORC and an ORC using thermal driven pump (TDP). It is established that the solar ORC using TDP has a superior performance to the conventional ORC under most working conditions. Results demonstrate that power output of the ORC using TDP ranges from 72 W to 82 W with the increase of evaporating temperature, which shows an improvement of up to 3.3% at a 100 °C evaporating temperature when compared with the power output of the conventional ORC. Energy and exergy efficiencies of the ORC using TDP increase from 11.3% to 12.6% and from 45.8% to 51.3% when the evaporating temperature increases from 75 °C to 100 °C. The efficiency of the ORC using TDP is improved by up to 3.27%. Additionally, the exergy destruction using TDP can be reduced in the evaporator and condenser. The highest exergy efficiency in the evaporator is 96.9%, an improvement of 62% in comparison with that of the conventional ORC, i.e., 59.9%. Thus, the small-scale solar ORC system using TDP is more promising for household application.

The oxidation behavior of ferritic–martensitic steels was investigated by exposure to 500 °C steam with a flow rate of 5 m/s. The oxidation kinetic curves followed near-parabolic rate equation and a type of Si modified steel SIMP displayed better oxidation resistance than T91. In the 5 m/s steam, the oxidation rate was significantly enhanced and the formation of hematite was also promoted at relatively low dissolved oxygen of 100 ppb. The results indicated that not only the alloy composition and dissolved oxygen but the flow rate played an important role in the corrosion behavior of ferritic–martensitic steels.

Deformation-induced martensites generally follow the principle on the selection of their variants in intrinsic crystallographic orientations with regard to the parent grains, which should be significantly affected by the cooperative rotation of the matrix. In this paper, the microstructural changes related to the deformation-induced transformation from metastable γ austenite to e and α′ martensites in 304 austenitic stainless steel upon uniaxial tensile loading at 180 K was investigated by employing in-situ synchrotron-based high-energy X-ray diffraction technique. The detailed information on low-temperature phase transformation kinetics was analyzed in terms of the grain rotation and the change in phase volume, stress partitioning, and dislocation density, which were further compared with experimental observations for the room temperature deformed specimen almost without stress-induced martensite. The elastic strain measured in the newly formed α′ martensite was quite low (only ~200 μɛ) upon tensile loading due to stress relaxation, evidencing the role of α′ martensite nucleation in strain accommodation. The minor statistical evolution of texture for all constituent phases, in combination with the martensitic variant selection principle, enables us to reveal the complex interactions of deformation and transformation, finding that the e martensite firstly originated in the [0 0 1]//LD-oriented grains of γ matrix, while α′ martensite was initially formed in the [1 1 1]//LD-oriented γ grains. Furthermore, the interplay of phases enhanced the grain rotation toward [0 0 1] during deformation at 180 K, which could be elucidated by the influence of transformed martensites on the specific selection of slip systems.

The high-pressure response of few-layer black phosphorus (BP) nanosheets remains elusive, despite the special interest in it particularly after the achievement of an exotic few-layer BP based field effect transistor. Here, we identified a pressure-induced reversible phase transition on few-layer BP nanosheets by performing in situ ADXRD and Raman spectroscopy with the assistance of DAC apparatus. The few-layer BP nanosheets transformed from orthorhombic semiconductors to simple cubic metal with increasing pressure, which is well interpreted using the pressure-induced inverse Peierls distortion. The obtained simple cubic BP nanosheets exhibited an enhanced isothermal bulk modulus of 147.0(2) GPa, and negative Grüneisen parameters that were attributed to the pressure-driven softening of phonon energies. Note that the simple cubic BP nanosheets adopted the highest symmetry which is in stark contrast to the general phase transformation under high pressure. First-principles calculations indicated that the metallic BP was significantly related to the band overlapped metallization, resulting from the traversing of density of states across the Fermi level at high pressure. Such findings paved a potential pathway to design targeted BP nanostructures with functional properties at extremes, and opened up possibilities for conceptually new devices.

Stimulated Raman scattering (SRS) of the aromatic CH stretching band is enhanced, and the frequency of C Br out-of-plane bending mode shifts upon laser-induced plasma generation in benzene–bromobenzene mixture. The effect of mixture ratio on the mechanism of SRS enhancement is attributed to the formation of cationic (benzene–bromobenzene)+ complexes under strong excitation conditions. When the volume ratio of benzene and bromobenzene is 1:2, the optimized trimer (bromobenzene–benzene–bromobenzene) leads to a shift of a Raman band, which could be due to the role of C H⋯Br hydrogen bond in the trimer. Results are consistent with Gaussian (EM64L-G09RevB.01) simulation data, which is performed at B3LYP/6-31G levels, which all geometries were fully optimized using the minimum analytical gradient method.

Phase change materials (PCMs) are frequently and widely used in latent thermal energy storage (LTES) system and thermal management (TM) system due to their large latent heats and capabilities of maintaining nearly constant temperature. However, the performances of PCMs in LTES and TM systems are seriously limited by their low thermal conductivities and poor heat transfer performances, which consequently stimulates intensive experimental and theoretical investigations on improving the thermal conductivities and heat transfer performances of PCMs by using different methods. The present paper reviews the recent progresses of the investigations and applications of the composite PCMs with the enhanced performance. The focuses are placed on the composite PCMs fabricated by using the metal foams and carbon materials, which have been proved to be the most promising approaches for thermal conductivity and heat transfer promotion on PCMs. The fabrication processes of the composite PCMs are first introduced in the present paper followed by the thermal characterization. The measurement of the effective thermal conductivities of the composite PCMs is discussed in detail by comparing different measuring methods, and the theoretical models to predict the effective thermal conductivities of the composite PCMs are also presented. The mathematical models describing the phase change heat transfer characteristics of the composite PCMs which are very important for system modeling and design are also addressed and discussed in the present review. Furthermore, the applications of the composite PCMs to LTES and TM systems are introduced and summarized by illustrating the typical examples. It can be understood that the composite PCMs can effectively improve the performances of LTES and TM systems, which therefore calls for the further investigation in this research field. Finally, the future research topics are suggested.

This work experimentally investigated adsorption equilibrium and reaction kinetics of ammonia adsorption/desorption on the composite of strontium chloride (SrCl2) impregnated into expanded graphite, and also discussed the potential influence of the addition of expanded graphite on the SrCl2-NH3 reaction characteristics. The measured and analysed results can be very useful information to design the system and operating conditions using the similar chemisorption composites. Equilibrium concentration characteristics of ammonia within the studied composite were measured using the heat sources at 90 °C, 100 °C and 110 °C for the decomposition process, where the degree of conversion achieved 50%, 78% and 96% respectively. Therefore, the equilibrium equation reflecting the relationship between temperature, pressure and concentration was developed, and a pseudo-equilibrium zone was found, which should be useful information to setup the system operating condition for the desired global transformation. It was suspected that the addition of expanded graphite altered the reaction equilibrium due to the pore effect and the salt-confinement. The concept of two-stage kinetic model was proposed and kinetic parameters were determined by fitting experimental data. The developed kinetic equations can predict dynamic cyclic performance of a reactive bed in similar geometric structure with reasonable accuracy. Such a chemisorption cycle using the SrCl2-expnaded graphite (mass ratio 2:1) composite can be used for cooling application, and the maximum SCP value can be achieved as high as 656 W/kg at t = 2.5 min, and the COP can be 0.3 after one hour of synthesis process under the condition of Tev = 0 °C, Tcon = 20 °C, Theat = 110 °C.

Smart materials which are capable of responding to external stimuli such as strain, temperature, electronic or magnetic fields have seen increasing demand from various fields of application. Mechanoluminescence (ML) is light emission phenomenon induced by external mechanical stimuli, which is often used to monitor and record the action of invisible forces in visible space. However, existing ML materials with limited spectral window has largely limited its applications. Extending ML operation to UV or near-infrared (NIR) regions would overcome this issue. In this work, materials with simultaneous visible to NIR ML is realized based on rare-earth (RE) ions doped CaZnOS, in particular, CaZnOS:Er3+ demonstrates ML on multiple spectral bands, including 510–538 nm, 538–570 nm, 640–680 nm, 845–880 nm, 960–1000 nm and 1450–1700 nm. Insight on the origin of ML in CaZnOS:RE3+ is discussed with the aid of in situ high-pressure studies. These observations indicate that the oriented migration of electrons which can be modulated or accelerated in a strain-induced piezoelectric field is a key in ML process. This interpretation provides a new tool for leveraging tailored ML performance in the further design of strain- and force-responsive materials.

Metal halide perovskites (MHPs) are of great interest for optoelectronics because of their high quantum efficiency in solar cells and light-emitting devices. However, exploring an effective strategy to further improve their optical activities remains a considerable challenge. Here, we report that nanocrystals (NCs) of the initially nonfluorescent zero-dimensional (0D) cesium lead halide perovskite Cs4PbBr6 exhibit a distinct emission under a high pressure of 3.01 GPa. Subsequently, the emission intensity of Cs4PbBr6 NCs experiences a significant increase upon further compression. Joint experimental and theoretical analyses indicate that such pressure-induced emission (PIE) may be ascribed to the enhanced optical activity and the increased binding energy of self-trapped excitons upon compression. This phenomenon is a result of the large distortion of [PbBr6]4− octahedral motifs resulting from a structural phase transition. Our findings demonstrate that high pressure can be a robust tool to boost the photoluminescence efficiency and provide insights into the relationship between the structure and optical properties of 0D MHPs under extreme conditions., The potential optoelectronic applications of metal halide perovskites make exploration and tuning of their optical properties of great interest. Here the authors show that non-emitting zero-dimensional cesium lead halide perovskites become strongly fluorescent under high pressure, due to distortion-induced effects.

In attempt to the obtain detailed geometric information of proton transfer compound (subsequently denote as SQBP) formed between squaric acid (SQ)and 4,4′-bipyridine(BP), and to investigate the mechanisms of pressure-induced double proton transfer and related structural phase transition, we carried out in-situ high pressure Raman spectroscopy of SQBP up to 20 GPa. A solid-solid phase transition together with double proton transfer phenomenon was confirmed by Raman spectroscopy at about 1.5 GPa, and the activation of C = O stretching mode in Raman spectra indicates a square-ring structure of SQ with four symmetric C = O bond formation. These results are further supported by first-principals calculations and in-situ high pressure infrared absorption spectroscopy. Additionally, Raman intensity analysis suggests that a higher-order phase transition with planar BP molecular structure occurred in the pressure range of 3~6 GPa. As a result, the π electron delocalization effect in BP dominated the intensity enhancement of C = O stretching mode in SQ. To the best of our knowledge, this is the first time observation of the intensity enhancement of proton donor’s normal modes induced by proton acceptor’s π electron delocalization.

Phase change material slurry is widely used in such applications as thermal energy storage and thermal management. Thermal conductivity of phase change material slurry is one of the most important thermo-physical properties that are necessary for system design and performance evaluation. In the present study, thermal conductivity of a phase change material slurry, tetra-n-butylammonium bromide (TBAB) clathrate hydrate slurry (CHS), is experimentally measured by using transient hot-wire method. The theoretical model of thermal conductivity measurement of phase change material slurry under the influence of phase change is proposed and numerically analyzed to obtain real thermal conductivity. It is found that phase change significantly affects the measurement of thermal conductivity in that the real thermal conductivity is smaller than that obtained directly from the experiments because phase change enhances heat transfer during the measurement. The smaller the solid fraction of TBAB CHS, the larger the influence of phase change on thermal conductivity is. Such effect is apparently ubiquitous, which should also be taken into consideration in thermal conductivity measurement of other phase change material slurries.

Crystallographic dislocation has been well-known to be one of the major causes responsible for the unfavorable carrier dynamics in conventional semiconductor devices. Halide perovskite has exhibited promising applications in optoelectronic devices. However, how dislocation impacts its carrier dynamics in the 'defects-tolerant' halide perovskite is largely unknown. Here, via a remote epitaxy approach using polar substrates coated with graphene, we synthesize epitaxial halide perovskite with controlled dislocation density. First-principle calculations and molecular-dynamics simulations reveal weak film-substrate interaction and low density dislocation mechanism in remote epitaxy, respectively. High-resolution transmission electron microscopy, high-resolution atomic force microscopy and Cs-corrected scanning transmission electron microscopy unveil the lattice/atomic and dislocation structure of the remote epitaxial film. The controlling of dislocation density enables the unveiling of the dislocation-carrier dynamic relation in halide perovskite. The study provides an avenue to develop free-standing halide perovskite film with low dislocation density and improved carried dynamics.

We investigate role of thermal conduction on the evolution and saturation of the m/n=2/1 resistive tearing mode (m and n are, respectively, the poloidal and toroidal Fourier mode numbers), by using a 3D toroidal MHD code (CLT). It is found that thermal conduction has great influence on pressure and current profiles, and further affects the dynamic evolution of the tearing mode. Our simulation results indicate that the linear growth rate of the tearing mode increases, but the saturation level of magnetic islands decreases with increase of thermal conductivity. With a small thermal conductivity, a flatten distribution of the thermal pressure inside magnetic islands leads to a large pressure gradient at the edge that drives a ballooning mode to be unstable. We further found that the radial electric field at the magnetic island boundary and the vortex-like flow inside the magnetic island lead to a poloidally asymmetric transport barrier and reduce the thermal conductivity at the magnetic island boundary, which contributes to formation of an internal transport barrier.

Tetra-n-butyl ammonium bromide clathrate hydrate slurry (CHS) is very promising for cold storage and energy saving in air-conditioning applications because of its appropriate phase-change temperature range of 0–12°C, reasonably large latent heat, and good fluidity. In this study, we experimentally investigate the flow and heat transfer characteristics during CHS generation in both an in-house-made annular channel heat exchanger and a commercial double-tube heat exchanger. Meanwhile, the visualization of the growth of the hydrate crystals is also carried out and the thickness of the crystal layer is estimated from the visualization results. It is concluded from the experimental results that the pressure drop and heat transfer coefficient play very important roles in CHS generation and the commercial double-tube heat exchanger is more effective for CHS generation.

The heat transfer characteristics of phase change material slurries, e.g. tetra-n-butyl ammonium bromide (TBAB) clathrate hydrate slurry (CHS) and microencapsulated phase change material (MPCM) slurry, flowing through the heated circular tubes under constant heat flux are investigated in the present paper. The continuity equation, momentum and energy equations for the phase change material slurry in tubes are solved to obtain the variation of the temperature of the phase change material slurry with time and along the flow direction. The temperature variation of TBAB CHS can be divided into two regions, while there are three regions for MPCM slurry due to the existence of supercooling state. The comparison between the calculated and measured results reveals that MPCM slurry is possibly not fully melted during the flow melting, leading to a shorter melting region and higher outlet temperature than those of calculated values based on the heat balance equations.

The flow and heat transfer characteristics of tetra-n-butyl ammonium bromide (TBAB) clathrate hydrate slurry (CHS) during its generation process in a double-tube heat exchanger (DHE) and the growth of crystal layer were investigated experimentally. During the generation, the formed crystals were easy to adhere to the heat transfer surface, and the present study was focused on the influences of such crystal layer on the pressure drop and heat transfer coefficient between the generating TBAB CHS and coolant in the heat exchanger. Pressure drops of TBAB CHS flowing through DHE without heat exchange were measured in advance to develop the corresponding friction factor correlations, and the comparison of the pressure drops during TBAB CHS generation process to those without heat exchange was conducted to obtain the effective thickness of the crystal layer. It was found that the thickness of the crystal layer increased as the heat transfer process going on. The crystal layer caused the enlargement of pressure drop and the drastic reduction of heat transfer performance due to the narrowing flow passage and large thermal resistance, respectively. The effective thermal conductivity of the crystal layer was also determined for the prediction of the heat transfer performance in the heat exchanger.